Recasting the Fay-Riddell formulae for computing the stagnation point heat flux

2000 ◽  
Vol 214 (2) ◽  
pp. 115-120 ◽  
Author(s):  
G Zuppardi ◽  
A Esposito
Keyword(s):  
Heat Flux ◽  
Stagnation Point ◽  
High Speed ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Total Enthalpy ◽  
High Enthalpy ◽  
Computing Procedure ◽  
The University ◽  
Made In

The Fay-Riddell formulae, used to compute the heat flux at the stagnation point of spherical bodies in very high speed, laminar flow and dissociating air, have been revived and recast. As these formulae were obtained by fitting a number of results of the original Fay-Riddell computing procedure, which suffered from inaccuracies concerning operative parameters, it is to be expected that these inaccuracies also influence the correctness of the formulae. A sensitivity analysis has been made in order to identify the most critical parameter. Recast formulae have been calibrated using the results of the improved version of the Fay-Riddell computing procedure and then validated both by numerical results of a Navier-Stokes code and by experimental data. For this purpose two sets of heat flux measurements have been made in HEBDAF (high enthalpy blown-down arc facility) at the University of Naples, matching the operating conditions of the formula for a frozen boundary layer and non-catalytic wall. Recast formulae are valid in the range of free-stream total enthalpy between 3 and 37 MJ/kg.

scholarly journals The design of a practical high-speed computing machine. The EDSAC

1948 ◽  
Vol 195 (1042) ◽  
pp. 274-279 ◽  
Keyword(s):  
High Speed ◽  
Relaxation Methods ◽  
Mathematical Equations ◽  
Mathematical Laboratory ◽  
Fundamental Equations ◽  
Physical Laws ◽  
The University ◽  
Computing Machines ◽  
Conventional Type ◽  
Made In

I would like to give a description of the high-speed electronic digital calculating machine now in an advanced stage of construction in the University Mathematical Laboratory, Cambridge, and known as the EDSAC (Electronic Delay Storage Automatic Calculator). Before doing this I will set forth some of the considerations underlying its design. It will be realized that the potential power of electronic digital computing machines is very great, and that they are likely to have a far-reaching effect on certain fields of scientific research. It is, for example, often possible to write down the mathematical equations governing a situation but not possible to treat them analytically. If any progress is to be made in these cases it must be by a direct numerical attack on the fundamental equations. There have in recent years been a number of examples of this method. I might mention Professor Hartree’s work on self-consistent fields and Professor Southwell’s relaxation methods. In both cases the equations expressing the physical laws appropriate to the problem are written down and an approximate numerical solution sought without any intervening analysis of the conventional type. This kind of method is in principle of wide application and power, and the reason why it has not been more generally applied is that the labour of carrying out the necessary numerical processes is too great

Aerodynamic Damping Predictions Using a Linearized Navier-Stokes Analysis

1999 ◽  
Author(s):  
Daniel Hoyniak ◽  
William S. Clark
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Operating Conditions ◽  
The Other ◽  
Navier Stokes ◽  
Turbine Cascade ◽  
Blade Loading ◽  
Operating Condition ◽  
Linear Cascade ◽  
Aerodynamic Damping

A recently developed two dimensional, linearized Navier-Stokes algorithm, capable of modeling the unsteady flows encountered in turbomachinery applications, has been benchmarked and validated for use in the prediction of the aerodynamic damping. Benchmarking was accomplished by comparing numerical simulations with experimental data for two geometries. The first geometry investigated is a high turning turbine cascade. For this configuration, two different steady operating conditions were considered. The exit flow for one operating condition is subsonic whereas the exit flow for the other operating condition is supersonic. The second geometry investigated is a tip section from a high speed fan. Again, two separate steady operating conditions were examined. For this fan geometry, one operating condition falls within an experimentally observed flutter region whereas the other operating condition was observed experimentally to be flutter free. For both geometries considered, experimental measurements of the unsteady blade surface pressures were acquired for a linear cascade subjected to small amplitude torsional vibrations. Comparisons between the numerical calculations and the experimental data demonstrate the ability of the present computational model to predict accurately the steady and unsteady blade loading, and hence the aerodynamic damping, for each configuration presented.

Sealing Technology: Rub Test Rig for Abrasive/Abradable Systems

2007 ◽  
Author(s):  
Ulrich Rathmann ◽  
Sven Olmes ◽  
Alex Simeon
Keyword(s):  
High Speed ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Test Rig ◽  
Visual Appearance ◽  
Major Interest ◽  
Rubbing Behavior ◽  
Blade Tip ◽  
Detailed Assessment ◽  
The University

Performance and efficiency optimization is one of the major tasks in the turbo machinery industry. Therefore efforts for scientific and technical improvements focus on optimization and reduction of losses. Secondary losses are of major interest because of their parasitic character related to stage efficiency and power output. One of these losses is over tip leakage of blades. Common practice is a minimization of this clearance with abrasive/abradable combinations. With this technique the blade tip (abrasive material) can rub into its counterpart (heat-shield, abradable material on casings or liners) and therefore minimize the operating tip-clearance. This technology is well established in compressor and turbine engineering since many years [1]. Field experience shows that abrasive/abradable systems do not always work as intended. In some cases rubbing conditions are reversed so that the intended abradable cuts into the abrasive. Any benefit on operating tip-clearance will then be minor at best or even negative. Rubbing behavior is difficult to predict, especially for new materials or geometries where no experience is available. In close cooperation with the University of Applied Sciences Rapperswil (Switzerland), ALSTOM has developed a test rig that allows simulating engine-operating conditions and therefore evaluate abrasive/abradable combinations before actual implementation into an engine. The rig is designed to reproduce circumferential velocities and incursion rates that are typical for gas turbine engines in the compressor as well as in the turbine. Forces and temperatures are measured as quantitative data, visual appearance and metallographic condition of test specimens are recorded as qualitative data that allow a more detailed assessment of material combinations and operating conditions. This paper describes the design of a high-speed wear rig facility to test single blade and fully shrouded rub configurations. In addition the validation of the test rig against real engine experience and knowledge is shown.

Aerodynamic and Heat-Flux Measurements With Predictions on a Modern One and 1/2 Stage High Pressure Transonic Turbine

2004 ◽  
Author(s):  
Charles W. Haldeman ◽  
Michael G. Dunn ◽  
John W. Barter ◽  
Brian R. Green ◽  
Robert F. Bergholz
Keyword(s):  
Heat Flux ◽  
Reynolds Number ◽  
High Pressure ◽  
Operating Conditions ◽  
Test Facility ◽  
Navier Stokes ◽  
Design System ◽  
Full Time ◽  
Pressure Data ◽  
Flux Data

Aerodynamic and heat-transfer measurements were acquired using a modern stage and 1/2 high-pressure turbine operating at design corrected conditions and pressure ratio. These measurements were performed using the Ohio State University Gas Turbine Laboratory Turbine Test Facility (TTF). The research program utilized an uncooled turbine stage for which all three airfoils are heavily instrumented at multiple spans to develop a full database at different Reynolds numbers for code validation and flow-physics modeling. The pressure data, once normalized by the inlet conditions, was insensitive to the Reynolds number. The heat-flux data for the high-pressure stage suggests turbulent flow over most of the operating conditions and is Reynolds number sensitive. However, the heat-flux data does not scale according to flat plat theory for most of the airfoil surfaces. Several different predictions have been done using a variety of design and research codes. In this work, comparisons are made between industrial codes and an older code called UNSFLO-2D initially published in the late 1980’s. The comparisons show that the UNSFLO-2D results at midspan are comparable to the modern codes for the time-resolved and time-averaged pressure data, which is remarkable given the vast differences in the processing required. UNSFLO-2D models the entropy generated around the airfoil surfaces using the full Navier-Stokes equations, but propagates the entropy invisicidly downstream to the next blade row, dramatically reducing the computational power required. The accuracy of UNSFLO-2D suggests that this type of approach may be far more useful in creating time-accurate design tools, than trying to utilize full time-accurate Navier-stokes codes which are often currently used as research codes in the engine community, but have yet to be fully integrated into the design system due to their complexity and significant processor requirements.

Stagnation point heat flux in hypersonic high enthalpy flow

Shock Waves ◽  
1992 ◽  
Vol 2 (1) ◽  
pp. 43-47 ◽  
Author(s):  
S. L. Gai ◽  
N. R. Mudford
Keyword(s):  
Heat Flux ◽  
Stagnation Point ◽  
High Enthalpy ◽  
Stagnation Point Heat Flux

Effect of High-Enthalpy Air Chemistry on Stagnation Point Heat Flux

2014 ◽  
Vol 28 (2) ◽  
pp. 356-359 ◽  
Author(s):  
D. Siva K. Reddy ◽  
Bijaylakshmi Saikia ◽  
Krishnendu Sinha
Keyword(s):  
Heat Flux ◽  
Stagnation Point ◽  
High Enthalpy ◽  
Air Chemistry ◽  
Stagnation Point Heat Flux

Aero-Thermal Optimization of Bladeless Turbines

2020 ◽  
Author(s):  
James Braun ◽  
Guillermo Paniagua ◽  
Francois Falempin
Keyword(s):  
Heat Flux ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
Wavy Surface ◽  
Navier Stokes ◽  
Pressure Losses ◽  
Power Extraction ◽  
Grid Points ◽  
Commercial Solver

Abstract The harnessing of mechanical power from supersonic flows is constrained by physical limitations and substantial aerodynamic losses. Bladeless axial turbines are a viable alternative to extract power in such harsh conditions without restricting the operating conditions. In this paper, we present a shape optimization of the wavy surface of bladeless turbines to maximize the power extraction, while minimizing convective heat fluxes and pressure losses. First, a baseline geometry was defined and an experimental campaign was carried out on the baseline wavy surface of the bladeless turbine at supersonic conditions in the Purdue Experimental Aerothermal Lab. Pressure, heat flux and skin friction measurements were compared with the Reynolds Averaged Navier Stokes results. Afterwards, the evaluation routine which consisted of the blade generation, grid generation, solving, and post-processing was implemented within an evolutionary optimizer with a multi-objective function to maximize the pressure force and minimize heat flux and pressure loss. Finally, a three-dimensional assessment in terms of power, heat load and pressure drop was performed for the best performing geometry with the commercial solver CFD++ of Metacomp. Turbulence closure was provided with the k-omega-SST turbulence model. The annular chamber of the bladeless turbine consisted of an unstructured mesh of approx. 8–10 million grid points.

Aerothermodynamic correlations for high-speed flow

2017 ◽  
Vol 821 ◽  
pp. 421-439 ◽  
Author(s):  
Narendra Singh ◽  
Thomas E. Schwartzentruber
Keyword(s):  
Heat Flux ◽  
Stagnation Point ◽  
High Speed ◽  
Direct Simulation Monte Carlo ◽  
Local Heat ◽  
High Speed Flow ◽  
Speed Flow ◽  
Wide Range ◽  
Correlation Parameters ◽  
Stagnation Point Heat Flux

Heat flux and drag correlations are developed for high-speed flow over spherical geometries that are accurate for any Knudsen number ranging from continuum to free-molecular conditions. A stagnation point heat flux correlation is derived as a correction to the continuum (Fourier model) heat flux and also reproduces the correct heat flux in the free-molecular limit by use of a bridging function. In this manner, the correlation can be combined with existing continuum correlations based on computational fluid dynamics simulations, yet it can now be used accurately in the transitional and free-molecular regimes. The functional form of the stagnation point heat flux correlation is physics based, and was derived via the Burnett and super-Burnett equations in a recent article, Singh & Schwartzentruber (J. Fluid Mech., vol. 792, 2016, pp. 981–996). In addition, correlation parameters from the literature are used to construct simple expressions for the local heat flux around the sphere as well as the integrated drag coefficient. A large number of direct simulation Monte Carlo calculations are performed over a wide range of conditions. The computed heat flux and drag data are used to validate the correlations and also to fit the correlation parameters. Compared to existing continuum-based correlations, the new correlations will enable engineering analysis of flight conditions at higher altitudes and/or smaller geometry radii, useful for a variety of applications including blunt body planetary entry, sharp leading edges, low orbiting satellites, meteorites and space debris.

scholarly journals Efficiency of disengaged wet brake packs

2018 ◽  
Vol 233 (6) ◽  
pp. 1562-1569 ◽  
Author(s):  
M Leighton ◽  
Nicholas Morris ◽  
Gareth Trimmer ◽  
Paul D King ◽  
Homer Rahnejat
Keyword(s):  
High Speed ◽  
Experimental Approach ◽  
Fuel Efficiency ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Navier Stokes ◽  
Fluid Viscosity ◽  
Fluid Inertia ◽  
Systems Model ◽  
High Fluid

Key objectives in off-highway vehicular powertrain development are fuel efficiency and environmental protection. As a result, palliative measures are made to reduce parasitic frictional losses while sustaining machine operational performance and reliability. A potential key contributor to the overall power loss is the rotation of disengaged wet multi-plate pack brake friction. Despite the numerous advantages of wet brake pack design, during high-speed manoeuvre in highway travel or at start-up conditions, significant frictional power losses occur. The addition of recessed grooves on the brake friction lining is used to dissipate heat during engagement. These complicate the prediction of performance of the system, particularly when disengaged. To characterise the losses produced by these components, a combined numerical and experimental approach is required. This paper presents a Reynolds-based numerical model including the effect of fluid inertia and squeeze film transience for prediction of performance of wet brake systems. Model predictions are compared with very detailed combined Navier–Stokes and Rayleigh-Plesset fluid dynamics analysis to ascertain its degree of conformity to representative physical operating conditions, as well the use of a developed experimental rig. The combined numerical and experimental approach is used to predict significant losses produced during various operating conditions. It is shown that cavitation becomes significant at low temperatures due to micro-hydrodynamic action, enhanced by high fluid viscosity. The magnitude of the losses for these components under various operating conditions is presented. The combined numerical-experimental study of wet multi-plate brakes of off-highway vehicles with cavitation flow dynamics has not hitherto been reported in the literature.

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